Photochromic composite material

Abstract

Sol-gel process for producing a photochromic composite material includes successive stages of hydrolysis, condensation, and drying, in which an alkoxysilane is selected as a precursor, and a ruthenium complex with a nitrosyl ligand is selected as a photochromic complex, and, in combination, the sol-gel process is implemented starting from the selected precursor and photochromic complex, with successive stages of hydrolysis, arrangement in a container of a selected shape, condensation, curing and aging, whereby this latter stage includes a final drying cycle, and for, the curing and aging stages, the pH, temperature and duration are selected so that in the produced xerogel, whose shape is determined by that of the container, the photochromic ruthenium complex with a nitrosyl ligand, in the crystalline state and in the form of nanoparticles, is inserted into the nanopores of the silica matrix, distributed in an at least substantially homogeneous way.

The invention claimed is: 
     
       1. A sol-gel process for the production of a photochromic composite material, comprising the steps of:
 selecting an alkoxysilane as a precursor, 
 selecting a ruthenium complex with a nitrosyl ligand is selected as a photochromic complex, and, in combination, 
 starting the sol-gel process by providing the selected precursor and the selected photochromic complex, with successive stages of hydrolysis, arrangement in a container of a selected shape, condensation, curing and aging, whereby a latter stage includes a final drying cycle, and 
 for the stages of curing and aging, pH, temperature and duration are selected so xerogel that is produced, whose shape is determined by that of the container, the photochromic ruthenium complex with the nitrosyl ligand, in a crystalline state and in form of nanoparticles, is inserted into nanopores of silica matrix, distributed in an at least substantially homogeneous way. 
 
     
     
       2. The process according to  claim 1 , wherein the precursor is selected from the group consisting of tetramethoxyorthosilane (TMOS), vinyltriethoxysilane (VTES), tetraethoxyorthosilane (TEOS), and alkoxides M(OR)x, wherein M is a metal and R is an alkyl group. 
     
     
       3. The process according to  claim 2 , wherein total hydrolysis of the alkoxide is achieved, with all of OR groups being replaced by OH groups. 
     
     
       4. The process according to  claim 2 , wherein the alkoxide is mixed with methanol, and the mixture is stirred. 
     
     
       5. The process according to  claim 1 , wherein the photochromic complex is selected from the group consisting of [RuCl(NO)(py) 4 ][PF 6 ] 2 .½H 2 O and [RuY(NO)(py) 4 ]X 2 , wherein Y is Cl, Br, or OH, and X is selected from the group consisting of Br, Cl, PF 6  and BF 4 . 
     
     
       6. The process according to  claim 1 , wherein stages of the sol-gel process are produced at mild temperature and pressure, close to ambient temperature and pressure. 
     
     
       7. The process according to  claim 1 , wherein after beginning of the hydrolysis stage, the selected photochromic complex in solution, is added to the precursor. 
     
     
       8. The process according to  claim 1 , wherein the selected photochromic complex in solution is used in water or, acetonitrile. 
     
     
       9. The process according to  claim 1 , wherein the container in the form of a tube or a flat-bottomed box is used, depending on whether it is desired to produce a monolith or a plate. 
     
     
       10. The process according to  claim 1 , wherein an acidic pH<7 is selected for the stages of curing and aging. 
     
     
       11. The process according to  claim 1 , wherein in presence of acetonitrile, the curing stage lasts on the order of one week at a temperature on the order of 55° C., in a closed atmosphere. 
     
     
       12. The process according to  claim 1 , wherein in presence of water, the curing stage lasts on the order of 72 hours at ambient temperature. 
     
     
       13. The process according to  claim 1 , wherein the aging stage lasts on the order of one week at a temperature on the order of 55° C. 
     
     
       14. A photochromic composite material produced by the process according to  claim 1 , wherein xerogel that is produced has a shape that is determined by that of the container and comprises the photochromic ruthenium complex with the nitrosyl ligand, in a crystalline state and in form of nanoparticles, is inserted into nanopores of silica matrix, distributed in an at least substantially homogeneous way. 
     
     
       15. The photochromic chromic composite material according to  claim 14 , wherein the photochromic composite material is in the shape of a monolith or in the shape of a plate of a desired thickness. 
     
     
       16. The photochromic composite material according to  claim 14 , wherein a mean size of the nanopores of silica matrix is between 2 and 15 nm. 
     
     
       17. The photochromic composite material according to  claim 14 , wherein most numerous particles of the photochromic complex nanocrystals are between 2 and 4 nm. 
     
     
       18. A high-quality optical memory medium comprising at least one photochromic composite material according to  claim 14 , wherein a photo-induced population of the at least one photochromic composite material is close to photochromic complex monocrystals. 
     
     
       19. An optical memory medium according to  claim 18 , wherein a temperature is close to the ambient temperature. 
     
     
       20. The optical memory medium according to  claim 18 , having a complete reversible change of color after irradiation. 
     
     
       21. The optical memory medium according to  claim 18 , having metastable states with a service life greater than 9 years.